Cross-connection Control for Wastewater Treatment Plants Department - - PowerPoint PPT Presentation

Cross-connection Control for Wastewater Treatment Plants

Department of Health Mission

We work with others to protect and improve the health of all people in Washington State.

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Presentation Overview

• Descriptions
• Requirements
• The Project
• Common Deficiencies

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Descriptions

Wastewater Treatment Plants

• Many of the wastewater treatment and collection

facilities are now old and worn, and require improvement, repair or replacement to maintain their useful life.

• The character and quantity of contaminants

presenting problems today are far more complex than those that presented challenges in the past.

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Wastewater Plant Schematic

Digesters RAS/WAS Pumps Secondary Clarifier Aeration Basin Head works Primary Clarifier Solids Handling

Backflow Incidents

• Hundreds of incidents documented

– USC CCC Manual (2009) – EPA’s CCC Issue Paper (2002) – PNWS-AWWA Incident Manual (1995)

• Incident impacts

– Health – Costs of investigation and clean-up – Litigation

• Incidents are under-reported

– Not detected or not reported

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Reported WA Backflow Incidents Cause and Number

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Number of Reports (1996-2017) 74 Caused by backpressure 51 Caused by backsiphonage 18 Unknown cause 5

• Corpus Christi and Chicago

BACKFLOW AT A WASTEWATER TREATMENT PLANT

• In December 1983, effluent from a wastewater

treatment plant in San Antonio, Texas, backflowed into the potable water system at the plant because of maintenance activities.

• Eight employees reportedly suffered

gastrointestinal problems. Fortunately, a reduced- pressure principle backflow-prevention assembly was in place at the water service connection to the plant. This assembly contained contamination within the plant site.

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Requirements

CCC at Sewage Facilities

Cross-connection control (CCC) at sewage facilities has two functions:

• Protecting the public potable water system

from contamination

• Protecting the onsite domestic potable water

system from contamination.

Basis

Three concepts form the basis for cross-connection control at sewage facilities.

• The public water supply is protected by premise

isolation RPBAs and RPDAs and in-plant air gaps.

• On-site domestic potable water is protected by

RPBAs and in-plant air gaps.

• Actual or potential connections to sewage, process

water or toxic chemicals are downstream of an air gap.

Potable Water

• Do not use potable water for purposes other than

drinking, personal hygiene and emergency washing facilities.

• Laboratory usage is permissible provided that the

laboratory supply line is fitted with an RPBA and, where appropriate, there are in-lab air gaps.

“Ideal” Situation

Complicated Situation

The Orange Book

• Must locate air gaps, RPBAs and RPDAs above

ground level

• Must locate premise isolation backflow preventer

adjacent to meter or property line

• Supply all hose bibs, wall hydrants, and yard

hydrants, whether above or below ground, interior or exterior, through an air gap

The Orange Book

“Facility designs must include a pressurized water system supplied through an air gap to facilitate cleaning or flushing of wet wells, dry wells, tanks, basins and equipment.”

Reclaimed water

• Must protect potable water from reclaimed

water as if reclaimed water were sewage

• Reclaimed water is protected as if reclaimed

water were potable water

Potable Water

• Recommended that designers locate all

potable water piping at ground level or above to prevent future inadvertent cross connection.

• Do not route city water/potable water piping

through wet well areas to prevent future inadvertent cross-connection.

Emergency Washing

• Designers should try not to locate emergency

washing facilities(eye wash stations/showers) below ground level.

• If designers cannot avoid locating emergency

wash stations below-ground must demonstrate that the installation will protect potable water supplies from accidental contamination.

Irrigation

• Irrigations systems may use non-potable water

taken downstream of a backflow preventer, disinfected plant effluent, reclaimed water or stormwater collected within the facility’s perimeter.

• Ecology discourages use of potable water for

irrigation; such use must include an RPBA.

Fire Protection

The water supply to any fire protection system must be equipped with an RPBA located and installed in accordance with the requirements for the premise isolation backflow preventer.

Chemicals and Substances

• Properly equipped water systems used with,

connected to, or have the potential to come into contact with hazardous chemicals and substances

• Proper equipment includes supplementary air

gaps and backflow prevention devices appropriate to the degree of hazard that would result if those chemicals were to backflow into the facility piping systems

Odor Control

• Odor control involves sewage aerosols and
• particulates. Water supplied to odor control

equipment or to hose bibs in the odor control area is considered to be in direct contact with sewage.

• Water supplied to odor control areas and

equipment must utilize an air gap.

WAC 246-290-490 (4)(b)

(ii) For service connections to premises posing a severe health cross-connection hazard including wastewater treatment plants, radioactive material processing plants, and nuclear reactors, the purveyor shall ensure that either an: (A) Approved air gap is installed for premises isolation; or (B) Approved RPBA or RPDA is installed for premises isolation in combination with an in- plant approved air gap.

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Project

Background

• Since 2007, ODW has collected cross-connection

control data from the largest community water systems on the status of backflow prevention at wastewater treatment plants.

• Water systems self-report their CCC data and

ODW has not independently verified the information reported

Project Goals

• Perform CCC hazard surveys of 47 severe health

hazard facilities

• Evaluate self-reported data for the associated

PWS

• Report findings to ODW, PWS, and the facility

surveyed

• Compile data to determine:

– Program effectiveness. – Guidance, training, and resources needed. – Compliance with regulations.

Process

• Contact the public water system CCS and

discuss project.

• Contact WWTP operator with PWS CCS to

discuss the project.

• Gather as much information as available to

review before the survey.

• Perform survey of the facility.
• Write survey report.
• Send report to all parties.

Findings

Deficiencies Total found in all plants Number of plants % Of Plants Improper air gaps (majority of problem was not enough distance between outlet and flood rim) 14 12 41% No RPBA prior to air gap 8 5 17% Moving RPBA for hydrant tested annually 3 3 10% Improper protection for Chemical Injection 4 3 10% RPBA's installed below ground 31 18 62% Access restricted 0% Potential spoolpiece connection 2 2 7% Improper protection for Pump seal water 4 4 17% Valves installed downstream of AVB 5 4 14%

Findings

Deficiencies Total found in all plants Number of plants % Of Plants No hosebib vacuum breaker 14 8 28% No RPBA for laboratory 12 9 31% Double check on hydrant construction 1 1 3% Non potable pipe before fire sprinkler 1 1 3% Complicated piping 1 1 3% Processed water to eye station 1 1 3% Washdown water not air gapped 4 4 14% Premise Isolation not at property line 2 2 7% Reclaimedan potable supplied to restroom 1 1 3%

Data

• 29 surveys have been performed
• 72 percent of facilities did not meet the

regulations

• All facilities were up to date on their backflow

assembly testing

• 88 percent of water systems coordinate with their

authority having jurisdiction

• 84 percent of systems have a Quality

Control/Quality Assurance Program

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Common Deficiencies

Spool Piece

RPBA Not at Property Line

Direct Connection to Sewer Line

Improper Assembly

Improper Assembly

Proper Air Gap

Air Gap Below Flood Rim

Improper Air Gap

Air Gap Below Ground

Air Gap Defeated

No Hose Bib Vacuum Breaker

No Hose Bib Vacuum Breaker

RPBA Located Below Ground

Improper Protection for Chemical Injection

Proper Labeling

Improper Labeling

Pump Seal Water

Pump Seal Water

Eye Wash Stations

Corroded Assembly

Odor Control Station

Auxiliary Water Supply

Access To Assemblies

Mystery Assembly

Unable to Maintain

Direct Cross Connections

Autoclave

Shut Off Valve Moved

Shut Off Valves Removed

Bypass

Valve Downstream of AVB

No HBVB

Old Service Line

References

• Department of Ecology, Criteria for Sewage

Works Design

• Washington Administrative Code
• Washington Department of Health/Office of

Drinking Water Guidance

• Uniform Plumbing Code Amended for

Washington State

• Manual of Cross connection Control (University
• f Southern California)
• AWWA (American Water Works Association)

Yellow Book

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Contact Information

Scott Hemingway Washington Environmental Training Center Director 253-288-3381 shemingway@greenriver.edu Bill Bernier Operator Certification and Training Distribution/CCC Advisor 360-236-3562 william.bernier@doh.wa.gov

Questions?

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